Oil pressure problem: 50% drop when hot.
Oil pressure problem: 50% drop when hot. Until the car warms up, I have 40 psi of oil pressure at idle, when it gets hot after a drive it is down to ~20 or a touch lower. Under load when cold it rises to ~60, and ~40 when hot. Any ideas on what this may be? Pickup o-ring? Bearings? I am using Mobil 5W-30.
The engine is a 347 with ross forged pistons, stock rods/crank with ARP hardware. I assembled the longblock myself and the pan/pickup/o-ring are new.
The engine is a 347 with ross forged pistons, stock rods/crank with ARP hardware. I assembled the longblock myself and the pan/pickup/o-ring are new.
That problem sounds exactly like the characterisitcs of having issues with the O-ring. When the oil is cold it not thin enough to slip through the o-ring but when hot the oil thins out and finds all leaks possible. I would take a look at the O-ring and see if there are any issues there. Good luck with it!
That problem sounds exactly like the characterisitcs of having issues with the O-ring. When the oil is cold it not thin enough to slip through the o-ring but when hot the oil thins out and finds all leaks possible. I would take a look at the O-ring and see if there are any issues there. Good luck with it!
Other o-ring problems I have heard of usually saw lower pressure than this, glad to hear you have seen this before. I will pull it apart and check it out. 
Yeah those O-rings are extremely sensitive and just the smallest nick or pinch can cause these kind of issues. I have seen a GM certified tech mess this up 3 times in a row, so its not easy!
its definately not easy....
let me ask this, did you replace the o-ring? or simply reinstall it? i have seen on numeruos occasions on different engines, where the o ring is reused, it gets torn or nicked upon REMOVAL, then when its installed, even when installed properly, it leaks.
let me ask this, did you replace the o-ring? or simply reinstall it? i have seen on numeruos occasions on different engines, where the o ring is reused, it gets torn or nicked upon REMOVAL, then when its installed, even when installed properly, it leaks.
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not trying to jack your thread here but I have a similiar problem. It has only done this a few times though. After a hard run it has dropped from the 50lbs that it is normally at to 20-25 lbs and I can here the motor ticking. Each time it has done it I have shut it down and let it cool for about a half an hour. When I start it back up it is fine. Anyone have any ideas? BTW and sorry for the ignorance what O-ring are you referring to? It did this twice before I modded the motor and once after. I changed the oil pump during the mods.
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my engine after sitting overnight will hold 50 psi with a melling hv pump. As the temp comes up to normal its around 40ish. Once oil temps get above 200 degrees, I've seen it get as low as 29 psi at idle. Oil temp was 230 though LOL, had some fun getting her that hot too. When oil temp is 190-209 my pressure is around 29-33. (The numbers are at idle, pressure climbs decent under normal acceleration and comes up with authority under wot.) Ive seen 70 psi before the engine was totally warmed up and when hot still see 50 under wot acceleration. Not sure if you have an oil pump issue or not, but like you have been told its easy to mess up the o ring. Throw a mechanical guage on there and check your readings. If they verify your concerns then you might want to consider checking her out. BTW I run 15w50 with a few qts of 5w30 so we'll call it 12w45 lol. I'm going to run 6 1/2 qts of mobil 1 15w50 when its time to chg due to the hotter weather is here. My car hates cold starts when the temps are down, so I'll go ahead and use mobil 1 5w30 for my fall/early spring oil.
Last edited by allngn_c5; Jun 4, 2010 at 01:45 PM.
not trying to jack your thread here but I have a similiar problem. It has only done this a few times though. After a hard run it has dropped from the 50lbs that it is normally at to 20-25 lbs and I can here the motor ticking. Each time it has done it I have shut it down and let it cool for about a half an hour. When I start it back up it is fine. Anyone have any ideas? BTW and sorry for the ignorance what O-ring are you referring to? It did this twice before I modded the motor and once after. I changed the oil pump during the mods.
Try switching to a heavier weight oil.
My car gets a little noisey after run hard one time here in the heat/humidity.
its definately not easy....
let me ask this, did you replace the o-ring? or simply reinstall it? i have seen on numeruos occasions on different engines, where the o ring is reused, it gets torn or nicked upon REMOVAL, then when its installed, even when installed properly, it leaks.
let me ask this, did you replace the o-ring? or simply reinstall it? i have seen on numeruos occasions on different engines, where the o ring is reused, it gets torn or nicked upon REMOVAL, then when its installed, even when installed properly, it leaks.
Mine did it stock...still doing it after a TSP ported pump, goes to about 30psi when hot, but has good pressure at WOT...so im my case...i dont care.
Last edited by SuperSlow02; Jun 5, 2010 at 07:15 PM.
Until the car warms up, I have 40 psi of oil pressure at idle, when it gets hot after a drive it is down to ~20 or a touch lower. Under load when cold it rises to ~60, and ~40 when hot. Any ideas on what this may be? Pickup o-ring? Bearings? I am using Mobil 5W-30.
The engine is a 347 with ross forged pistons, stock rods/crank with ARP hardware. I assembled the longblock myself and the pan/pickup/o-ring are new.
The engine is a 347 with ross forged pistons, stock rods/crank with ARP hardware. I assembled the longblock myself and the pan/pickup/o-ring are new.
In any case, will switching to a thicker oil fix the problem or is it just a bandaid?
